1. Field of the Invention
The invention relates to a switching device, more particularly to a switching device that can provide a high degree of electrical stability.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional switching device 1 includes a rectangular casing 11, two metal terminal plates 12, a slide unit 13, a biasing unit 14, and a top cover 15.
The casing 11 is made of plastic, and includes front, rear and bottom walls 115, 113, 111, and two opposite lateral walls 112 between the front, rear and bottom walls 115, 113, 111. The front, rear, bottom and lateral walls 115, 113, 111, 112 cooperate to define a receiving space 116. A limiting groove 114 is formed in the bottom wall 111.
The metal terminal plates 12 are embedded respectively in two opposite sides of the bottom wall 111.
The slide unit 13 includes a plastic slide block 131 mounted slidably within the receiving space 116, and two metal conductive pieces 132 fixed respectively to two opposite sides of the slide block 131. The slide block 131 and the conductive pieces 132 are assembled by insert molding. The slide block 131 has a press portion 1311 projecting outwardly from the casing 11, and a slide portion 1312 located within the receiving space 116. The slide portion 1312 has a planar bottom face in contact with a groove surface of the limiting groove 114, and is restricted to slide along the limiting groove 114.
The biasing unit 14 is sleeved on the slide block 131 for biasing the same toward a non-conductive state.
The top cover 15 is provided to cover the casing 11.
In use, the press portion 1311 of the slide block 131 is operated so as to move the conductive pieces 132 between a conductive state, where the conductive pieces 132 contact electrically the respective terminal plates 12, and a non-conductive state, where the conductive pieces 132 are not in electrical contact with the respective terminal plates 12.
Although the aforementioned conventional switching device 1 can achieve its intended purpose, it has the following disadvantages:
1. Since the slide block 131 and the conductive pieces 132 are assembled by insert molding, during manufacture of the slide unit 13, the conductive pieces 132 are first positioned in a mold, after which a plastic material is injected into the mold to form the slide block 131. Such an insert molding process consumes much time, thereby increasing costs. Furthermore, when the conductive pieces 132 are inserted into the slide block 131 during insert molding, they deform easily. This adversely affects manufacturing productivity of the slide unit 13.
2. Since the bottom face of the slide portion 1312 is in direct contact with the groove surface of the limiting groove 114, the slide portion 1312 produces a large friction with the groove surface of the limiting groove 114 when it slides along the limiting groove 114. This results in significant wearing of these components, thereby shortening the service life of the conventional switching device 1.
3. Since the slide portion 1312 is not fitted exactly in the limiting groove 114 so that gaps 2 exist between the slide portion 1312 and the limiting groove 114, when the press portion 1311 is improperly operated, the slide portion 1312 tends to deviate either to the left or to the right, thereby destabilizing electrical connections between the conductive pieces 132 and the terminal plates 12.